Such a device is known by virtue of FR A 2 485 117, equivalent to U.S. Pat. No. 4,304,523. In this document, the end plate is designed to prevent the axial displacement of blades of the fir tree root type, the feet of which are mounted in axial notches provided on the periphery of the rotor disc. In order to mount the end plate, the split annular ring is firstly placed in the recess in the disc, after which it is radially compressed towards the inside of the recess by means of tools bearing upon the peripheral wall of the ring, until these tools come to bear upon the collar of the disc. Next, the base of the end plate is slid along the radially outer wall of the recess.
An axial force is exerted against the end plate in order that the foot comes to bear against the inside radial wall of the recess. The tools which compressed the annular ring are then slackened and the latter expands radially outwards.
Next, the axial force exerted upon the end plate is relieved. The ring has at its axially inner end a peripheral rabbet, in which the radially inner portion of the foot finds accommodation. The outer diameter of the ring is less than the inner diameter of the base of the end plate in order to allow the disengagement of the compression tools during assembly and their introduction during possible disassembly. The diameter of the bore in the foot of the end plate is greater than the diameter of the collar to allow the introduction of the inside portion of the end plate into the recess around the compression tools bearing against the periphery of the collar.
Since the end plate is subjected to axial stresses in the event of impacts upon the blades resulting from the ingestion of debris, which stresses are absorbed by the retaining ring, shearing torques are generated upon the ring owing to diameter deviations between the bore in the foot and the collar. This requires the retaining ring to be solid, yet sufficiently flexible to allow its compression and installation in the recess. The manufacture of this ring calls for costly machining.
FR 2 812 906 has proposed a modified retaining ring which, on the periphery of its outside radial face, has a chamfer which allows the said ring to be automatically compressed as the foot of the end plate passes through in the course of assembly. This foot comprises notches to allow the introduction of compression tools for the ring for disassembly purposes. This ring is also solid and calls for costly machining.
It should be noted that the retaining ring remains in the recess whilst the end plate is disassembled for the repair or replacement of a blade, for example. This ring is thus different from a traditional circlip, which is expanded by means of a part in order to be fitted around a shaft and which retracts elastically into a groove made in the periphery of the shaft.